1. Field of the Invention
The present invention relates to a system for scheduling an event in a device such as printing devices which print images on a recording medium. For example, the present invention is a printer which utilizes a date/time stamp downloaded from a host processor in order to schedule a process function in the printer.
2. Description of the Related Art
Due to the popularity of the personal computer for personal and home office use, manufacturers of personal printers strive to make ink jet printers which are both portable and which produce quality images, all at an affordable price. To accomplish this goal, some ink jet manufacturers have eliminated many hardware and processing features, found in larger ink jet printers, in the personal ink jet printer so as to reduce the cost and to limit the size of the ink jet printer intended for the home or home office.
One method of reducing the amount of hardware, processing and overall cost of a personal ink jet printer, is by producing a xe2x80x9cdumbxe2x80x9d printer which relies on the host processor to perform various print related processing and to operate various functions of the printer via commands. While it is possible to eliminate most of the processing features typically found in larger ink jet printers, one processing feature which has not been successfully eliminated from the ink jet printer is scheduling the print head cleaning process. That is, in order for ink jet printers to perform properly, ink jets (e.g., nozzles) in each of the print heads must be cleaned periodically. However, due to the portability of an ink jet printer, there is no way to guarantee that the ink jet printer will be connected to the same host processor that will maintain a schedule throughout the printer""s life time. As a result, a cleaning schedule from a particular printer remains stored in that printer.
One way of addressing the foregoing problem is by scheduling ink jet cleaning solely around events, such as a hard or soft power-on, print head replacement, loading of paper, etc. However, relying solely on events tends to be both wasteful of ink and unreliable since there is no way to guarantee how often the print heads will be cleaned.
Accordingly, it is desirable for an ink jet printer to maintain its own cleaning schedule while at the same time reducing the cost of the ink jet printer by eliminating unnecessary hardware, such as a real-time battery operated clock, thereby making the ink jet printer affordable. Heretofore, it has not been possible to rely on a host processor to provide the cleaning schedule so as to eliminate this feature from the ink jet printer itself.
The same problem arises in a device such as a printer of another type, for example, cleaning a toner in a laser printer, and so on.
The present invention addresses the foregoing problems by eliminating the need for a battery operated real-time clock from the printer and by relying on date/time (date and/or time) stamps which are downloaded by the host processor at predetermined times, such as when the host computer goes online, before every print job, etc. In this manner, the ink jet printer can calculate elapsed time by comparing the downloaded date/time stamps with the last date/time stored in the printer""s nonvolatile memory, such as an EEPROM, with the last time each print head has been cleaned. Based on this comparison, for example, an ink jet printer can determine when to clean each of the print heads. The event cleanings will in turn reset the elapsed time cleaning schedule.
In addition to elapsed time scheduling, the present invention addresses cleaning schedules by combining cleaning of print heads based on certain events, such as replacing a print head, performing a hard power-on, a soft power-on, etc. In addition, the printer will perform a cleaning operation in response to a user command to perform a print head cleaning.
Thus, according to one aspect, the present invention is an ink jet printer which includes an interface for interfacing with a host processor and for receiving print data, print commands, and real time/date information from the host processor, a memory for storing the print data, print commands and real time/date information, a print engine for printing an image in accordance with the print data and print commands, the print engine controlling at least one print head to print the image, and a processor for controlling processing events of the print engine based on the real time/date information received via the interface from the host processor and based on printer-related events.
According to another aspect, the present invention is a method for scheduling cleaning of an ink jet print head, the method including the steps of receiving real time/date information from an external source, storing the real time/date information in a volatile memory, storing, in a non-volatile memory, a last cleaning time for at least one print head in the ink jet printer, calculating an elapsed time by subtracting the stored real time/date information and the stored last cleaning time, comparing the calculated elapsed time to a predetermined elapsed time, and controlling the at least one print head to perform a cleaning process in the case the calculated elapsed time is greater than or equal to the predetermined elapsed time and storing, in the non-volatile memory, the latest last time for cleaning the at least one print head. However, in the case that the calculated elapsed time is less than the predetermined elapsed time, the method for scheduling cleaning awaits until either a comparison between a next down loaded time and last cleaning time, an elapsed internal time or the occurrence of a cleaning event, whichever comes first, in order to determine if a cleaning should be performed.